Method of modification in oil reservoirs using resident microorganisms and nutrient supplementation through biological wettability alteration

ABSTRACT

A method for improving oil recovery includes determining a specific nutrient package or formulation for stimulating and altering resident microorganisms to increase wettability of reservoir rock formations in oil reservoirs. Once determined, the specific nutrient package is applied to the oil reservoir to stimulate the resident microorganisms. The stimulating application is followed by a period of nutrient limitation where the physiology and surface characteristics of the resident microorganisms are altered. Once altered, the resident microorganisms interact with the reservoir rock formations to change the adhesion tension of the reservoir rock formation to a more water wet condition so that oil will flow more freely rather than be bound to the rock surface.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/33 6,353 filed Jun. 18, 2013

BACKGROUND OF THE INVENTION

This invention relates to the process of using resident microorganismsto change the wettability of oil field reservoirs. More particularlythis invention contemplates a mechanism for recovering otherwiseunrecoverable oil using a method of manipulating resident microorganismsin a reservoir through nutrient supplementation and then nutrientlimitation to induce physical and metabolic changes that lead to anincrease in oil recovery by changing the wettability in the impactedportions of the reservoir to a more water-wet condition.

SUMMARY OF THE INVENTION

A method for improving oil recovery includes determining a specificnutrient package or formulation for stimulating and altering residentmicroorganisms to change wettability of reservoir rock formations in oilreservoirs. Once determined, the specific nutrient package is applied tothe oil reservoir to stimulate the resident microorganisms. Thestimulating application is followed by a limiting period where thephysiology and surface characteristics of the resident microorganismsare altered. Once altered, the resident microorganisms interact with thereservoir rock formations to change the adhesion tension of thereservoir rock formation to a more water wet condition so that oil willflow more freely rather than continue being hound to the rock surface.

BRIEF DESCRIPTION OF THE FIGURE

The FIGURE is a flow diagram of a method of enhancing oil recovery.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A method is disclosed to increase oil recovery from oil reservoirs ofall types including, but not limited to, sandstone, carbonate,conglomerate, shale, siltstone or other rock-type exhibiting oil-wet ormixed wettability characteristics. The method contemplates the recoveryof oil from subsurface oil reservoir by modifying the characteristics ofresident microorganisms found in the oil reservoir.

The method includes the application of a specific nutrient formulationto modify and/or stimulate some of the resident microorganisms tointeract with oil contained In reservoir rock formations. Preferred isthe application of a specific package of nutrients in a liquid form thatcan be diluted to produce a range of concentrations from 100 grams perliter to 0.0001 grams per liter in the treated volume. The delivery ofthe nutrient formulation occurs via water injection wells or producingwells. In one embodiment the nutrient is a digest or extract of proteinand/or an organic cell extract of prokaryotic or eukaryotic ceils. Inone form, the nutrient formulation stimulates desirable residentmicroorganisms and suppresses some undesirable resident microorganisms.

Specific nutrient formulations facilitate microbe-mediated oil releasein reservoirs over a wide range of temperature and salinity that arecompatible with biological life. In one embodiment, the inventioncontemplates use of a series of analyses that lead to formulation of aspecific nutrient package to perform a microbiological response analysisunder actual reservoir conditions of the resident population ofmicroorganisms with the intent of refining the treatment of a reservoirto optimize changes in the resident microorganisms to take advantage ofhydrophobic properties that induce the recovery of oil though alteredwettability.

The step of stimulation of targeted resident microorganisms is followedby specific nutrient limitation that alters the physiology and surfacecharacteristics of the targeted microorganisms. This cycle of nutrientsupplementation and depletion may be repeated. In one embodiment thismodification of the resident microorganisms includes changes in cellsize or hydrophobic properties of reservoir fluids that altersurface-active properties. Typical reductions in the microorganism cellvolume is 50% or more, The steps of stimulation and modification of theoil interactive properties of the resident microorganisms is to a level,which enhances oil recovery. The surface active properties are such thatassociated wettability is changed such that adhesion tension is changedso the water more readily spreads and adheres to the reservoir rocksurfaces. In one embodiment a genetic analysis of residentmicroorganisms in produced water is included in the method to aid in thedetermination of the presence of the oil interactive microorganisms withthe capacity to alter wettability.

DEFINITIONS

“Wettability” is described as the adhesion tension. It is a function ofthe interfacial tension and determines which fluid (oil or water) willpreferentially wet (adhere to) the solid surface of the reservoir rock.If the adhesion tension is large, the denser phase liquid will readilyspread out and tend to coat the surface of the reservoir rock. If theadhesion tension is small, the denser fluid will only be weaklyattracted to the surface. By changing the reactive character to a morewater wet condition, oil will flow more freely rather than being boundto the rock surface. (Amyx, Bass and Whiting, Petroleum EngineeringPrinciples, McGraw-Hill, 1960)

“Resident Microorganisms” are defined as microorganisms that occur inoil reservoirs, prior to the envisioned treatment, irrespective of themicroorganism's origin or where they occur within the oil-bearingstrata.

What is claimed:
 1. A method of improving oil recovery, comprising thesteps of: applying a specific nutrient formulation to stimulate residentmicroorganisms in oil reservoir rock formations; limiting availabilityof the specific nutrient formulation to alter the physiology and surfacecharacteristics of the resident microorganisms; and allowing the alteredmicroorganisms to interact with the reservoir rock formations to changeadhesion tension of the reservoir rock formations to a more water wetcondition to allow oil to flow more freely.
 2. The method of claim 1further comprising the step of conducting a series of analyses todetermine the contents of the specific nutrient package.
 3. The methodof claim 1 wherein surface-active properties of the residentmicroorganisms are modified.
 4. The method of claim 1 wherein cellvolume of the resident microorganisms are reduced by fifty percent ormore.
 5. The method of claim 3 wherein interfacial tension and relativepermeability of the surface-active properties are changed.
 6. The methodof claim 1 wherein the specific nutrient package is in liquid form anddiluted in a treated volume in a concentration range between 100 gramsper liter and 0.0001 grams per liter.
 7. The method of claim 1 whereinthe specific nutrient formulation facilitates a microbe-mediated oilrelease in reservoirs up to 130 c and 150,000 ppm total dissolvedsolids.
 8. The method of claim 1 wherein the specific nutrientformulation stimulates desirable resident microorganisms and suppressundesirable resident microorganisms.
 9. The method of claim 1 whereinthe delivery of the specific nutrient formulation is selected from agroup consisting of water injection wells, producing wells, and disposalwells.
 10. The method of claim 1 further comprising the step ofconducting genetic analysis of the resident microorganisms to determinewhether oil interactive microorganisms capable of altering wettabilityare present.